is never selected but the clutch has been depressed long enough for the engine to lose speed, the system will bring the engine back to speed for the same gear if the driver begins to raise the clutch. If the shifter is moved to a higher gear and the clutch is re-engaged quickly, the system will let the natural deceleration of the engine sync the drive train with the higher gear. If the clutch is depressed long enough for the engine to fall below the speed of the higher new gear, the computer will blip the throttle to bring the engine back to speed. Most usefully, if a new, lower gear is selected, the computer will accelerate the engine to the new estimated speed, even to the point of redline. In all cases, the computer continues to adjust the throttle to match the ever-changing target speed of the wheels when the clutch is partially engaged, as the vehicle speed may often change while shifting (for example due to shifting while going up or down a hill). In actual execution, the computer is able to "blip" the throttle due to the presence of an electronic throttle, in which the computer has direct control over both the fuel and air inputs to the engine. As the accelerator pedal in such a system has no direct mechanical connection to the throttle valve, the engagement of the system to change engine speeds is apparent to the driver via sound and tachometer cues only, and the feel or weight of the accelerator pedal remains constant. Regardless of the previous operation, the involvement of the system is ended when the clutch pedal reaches a certain point of re-engagement to ensure the system does not interfere with the driver's intended power output to the wheels. In any case, Nissan has provided a switch to disengage the system, for example in the case of the driver preferring to perform their own rev-matching. Nissan